Hydraulic control system



Oct. 16, 1962 J. H. PROVINCE 3,058,426

HYDRAULIC CONTROL SYSTEM Filed Jan. 3, 1958 2 Sheer.s-5heerI l 2Sheets-Sheet 2 Filed Jan. 5, 1958 INVENTOR 1.H. PROVINCE BY n,

ATTORNEYS.

United States Patent Olifice 3,058,426 Patented Oct. 16, 1952 3,058,426RAUIJIC CNTROL SYSTEM John H. Province, Bartlesville, kla., vassigner toPhillips Petroleum Company, a corporation Delaware Filed Jan. 3, 1958,Ser. No. 707,024 3 Claims. (Cl. 103-17) This invention relates to acontrol system for hydraulic pumps. In one aspect it relates to ahydraulic system to operate -pipe tongs, rotary air couplings, derricks,and other equipment. In another aspect it relates to an irnproved meansof control of a prime mover or motor for providing power for operatingthe above-mentioned equipment.

In oil well servicing operations it is common practice to obtain thepower needed to operate the hoist winch, tubing tongs and other unitsfrom the truck motor. Modern well servicing units often employ hydraulicpumps for the operation of derr'icks and other equipment. Thus, asuitable hydraulic pump normally is available on a servicing rig. Forthis reason I operate a derrick hoist, tubing tongs, and other equipmenthydraulicially. The hydraulic pump employed to energize the tubing tongsand other equipment is frequently driven by the same truck motor whichenergizes the hoisting winch. This dual functioning of the motor createscertain difliculties because the motor must be operated at aconsiderably higher speed when operating the winch than when coupled tothe hydraulic pump. In order to prevent the hydraulic pump from beingdriven at an excessively high speed when the engine is driving thewinch, a pneumatically operated clutch system is provided to disengagethe drive shaft of the truck from the hydraulic pump when the speed ofthe motor exceeds a predetermined value. An air coupling is employed inthe clutch system.

Accordingly, it is an object of this invention to provide an improvedcontrol system for use with a well servicing rig.

Another object is to provide an improved control system to operatetubing tongs and other equipment from the source of hydraulic fluidunder pressure.

Another object of this invention is to provide an automatic controlsystem for operating the prime mover or motor which drives a hydraulicpressure iluid pump to increase the motor and pump speed underconditions requiring large volumes of high pressure actuating fluid.

Yet another object of this invention is to provide such an automaticcontrol system which is responsive to hydraulic pressure for increasinghydraulic pressure fluid ilow for operating a hydraulic unit requiring alarge volume of pressure fluid.

Other objects, advantages and features of this invention will becomeapparent from the following detailed description which, taken with theattached drawing, forms a part of this specification.

In the drawing FIGURE 1 is a schematic representation of a preferredembodiment of the control system of this invention.

FIGURE 2 is a longitudinal view, partly in section, of a portion of theapparatus of FIGURE 1.

FIGURE 3 is an elevational view, partly in section7 of a normally closedpressure switch of FIGURE 1.

FlGURE 4 illustrates in diagrammatic form, a pair of electrical contactssuitable for substitution in the housing illustrated in FIGURE 3 toprovide a normally open pressure switch.

FIGURE 5 is an elevational view, partly in section, of a solenoid valveof FIGURE 1.

Specifically, my invention is directed to a control system to regulatethe speed of a variable speed driving member comprising in combination,a hydraulic lluid pump driven by said driving member, means forcontrolling flow of actuating fluid to said driving member, a source ofelectromotive force, an electrical circuit for communication ofelectromotive force from said source to said means, a conduit fortransmitting pressure fluid, said pump being adapted to pressure `saidpressure fluid through said conduit, a pressure switch, the switch ofsaid pressure switch being disposed in said electrical circuit, thepressure sensing element of said pressure switch being in operativecommunication with pressure iluid in said conduit, said pressure sensingelement being adapted to close said switch in response to an increase ofpressure of said pressure fluid in said conduit above a predeterminedpressure thereby actuating said means to increase ilow of actuatingfluid to said driving member and said pressure sensing element beingadapted to open said switch in response to a decrease in pressure ofsaid pressure fluid in said conduit below said predetermined pressure tothrottle flow of actuating fluid to said driving member.

Referring now to the drawing and specifically to FIG- URE 1, referencenumeral 10 identities a truck motor which is employed to energize a wellservicing unit. The speed of a motor is controlled by a butterfly valvein carburetor 11. This valve is positioned by a pneumatically operatedcontroller 13. This controller 13 is actuated by pressure air suppliedfrom the storage tank 14. Tank 14 is connected to an air compressor, notshown, by a line 15. A line 16 extends from tank 14 to the inlet of athrottle valve 17. Air inlet in controller 13 is connected to tank 14through a line 18 provided with a 3-way solenoid operated valve 23. Theoutlet of throttle valve 17 is connected to a second air inlet 111 ofcontroller 13 by a line 21. Solenoid valve 23 is controlled by asolenoid 24 which is energized from a voltage source 25. One terminal ofvoltage source 25 is connected to ground as is one terminal of solenoid24. The second terminal of voltage source 25 is connected to a secondterminal of solenoid 24 by a lead wire 27 provided with a switch 28.Switch 28 is a manually operable switch. A line 22 communicates valve 23with the atmosphere for venting purposes. In the absence of power, thatis, when switch 28 is open, a line 19 communicates through valve Z3 andlines 13 and 16 with tank 14. When solenoid 24 is energized, by closingswitch 28, line 19 communicates through valve 23 and line 22 to theatmosphere.

The drive shaft of engine 10 is connected through a suitable powertake-oft" 29 and a shaft 311 to one member of a clutch 31. A `secondmember of clutch 31 is connected by a shaft 32 through a coupling orswivel 34 to a hydraulic pump 33. Clutch 31 is engaged by theapplication of pneumatic pressure thereto through coupling 34. Airpressure for energizing clutch 31 is supplied from a second storage `35which is connected to line `15 by a line 36 provided with a pressurereducing valve 37. The pressure in tank 35 is less than the pressure intank 14. Tank 35 is connected to coupling 34 by a line 3S having asolenoid operated 3-way valve 39, conduit 38a, an oiler 40, a conduit3811, a quick release valve 41 and conduit 38e. Valve 39 is energized bya `solenoid 43 which has one terminal connected to the ground. Thesecond terminal is connected to the second terminal of voltage source 25by a lead 44 which is provided with a manually operated switch 46 and anormally closed pressure operated switch 47. Pressure switch 47 iscontrolled by the pressure from line 21 through a line 48, pressureabove a predetermined value opening the electrical switch 47 and belowthis value allowing the switch to close.

The quick relief valve 41 is a standard 3-way quick relief valve, morefully illustrated on pages 133 and 134 of the Bendix-WestinghouseMaintenance Manual Number B-W 1116 published in 1952` by theBendix-Westinghouse Automotive Air-Brake Company. This valve 41 is notnecessary to the operation of the system and may be dispensed with, itsmain purpose being to allow air to vent to the atmosphere throughopening 41a (when open) faster than it could vent through line 381;,oiler 40, line 38a, valve 39 and vent line 39a, thereby yallowing clutch31 to release quickly without slipping thereby reducing frictional `wearduring releasing. Valve 41 consists of a body having a chamber (notshown) with an air supply inlet and preliminary exhaust line 38b, aquick nir release outlet opening 41a disposed opposite 38b, and a line38C connecting one side of the chamber to clutch 31. There is a valveseat around 38h and 41a in the chamber, 4and a valve head having aflexible yannular rim is biased by a spring cord. When pressure in 38bis high, the valve head closes opening 41a and air from 38b passes theliexible rim into line 38C to engage clutch 31. When pressure in clutch31 kbalances the high pressure in 38.6, the flexible rim closes 38bwhile the valve head closes 41a. When pressure in 38b falls below thatin 38C, the valve head unseats, aided by the spring, opening outlet41ato clutch line 38C allowing quick release of air to the atmosphere.When high pressure returns to line 3Sb, the valve head closes opening41a and pressure air passes the flexible rim into 38C repeating thecycle.

As mentioned, valve 41 is not necessary, and may be eliminated as wheneither one of electrical switches 46 or 47 is open, solenoid 43 movesvalve 39 to connect line 38a to vent line 39a and air is released to theatmosphere through line 381;, oiler 40, line 38a, valve 39 and vent line39a, while valve 39 is closed to line 38. When both switches 46 and 47are closed, solenoid 43 actuates valve 39 to close vent line 39a andconnect line 38 and 38a, supplying air under pressure from tank to valve41 and line 38C to clutch 31 to engage said clutch.

The inlet of pump 33 is supplied with hydraulic iluid ,from an oilstorage tank 50 by a line 51 provided with a iilter 52. A lluid leakageline 49 returns leakage oil from pump 33 to tank 50. The outlet of pump33 is connected by a line 53 to a iirst port 54 of a valve 55. A secondport 56 of valve 55 is connected with a rst port 57 of a second valve 58by a line 59. The second port 60 of valve 5S is connected by a line 61to a first port 62 of a third valve 63. A second port 64 of valve 63 isconnected by a line 66 to a fluid opening 69 of a hydraulic motor 67.Motor 67 is connected with a gear box 68 which drives a tubing tongs,not sho-wn. A second fluid opening 70 of motor 67 -is connected by aline 71 to a third port 73 in valve 63. A fourth port 74 in valve 63 isconnected by a line 76, a check valve 77 and a line 78 through a thirdport 80 of valve 58. The fourth port 81 of valve 58 is connected bylines 82 and 83 to the oil tank 50. Ports 80 and 74 of respective valves58 and 63 are connected by line 78, a centering valve 85 and line 76. Athird port 87 in valve 55 communicates through a line 88 to supplyhydraulic fluid to other apparatus, not shown, Which may be employed onthe rig. The fluid supplied by line 88 is returned through a line 89 andline 83 to supply tank 50. The fourth port 90 of valve 55 is alsoconnected to return line 83 by' a line 91. Line 59, which connects ports56 `and 57 of the respective valve 55 and 58, is connected to tank 50 bya line 92 provided with a pressure relief valve 93. The connectionbetween the ports in valve 55, 58 and 63 are described hereinafter.

The valves S5, 58, 63 and tubing tongs, not shown, are fully describedin U.S. Patent 2,780,950 over which this present application is animprovement.

Air coupling or swivel 34 and clutch 31 are also described in detail inPatent 2,780,950. The purpose of coupling 34 is to introduce air fromline 38 to FIGURE 4 1 into a passage in shaft 32. This air pressure inturn actuates clutch 31 to connect shafts 30 and 32.

It might be stated that valves 58 and 63 are very similar to valve 55.The centering va-lve mentioned above, is also fully described in Patent2,780,950.

The tubing tongs described in said patent are power tongs which areadapted to be energized by hydraulic motor 67 in accordance with theprocedure Ifully described in said patent.

An electrical circuit 27a is provided for connecting voltage source 25with solenoid 24. This circuit 27a is provided with a manually operableswitch 103 and a pressure actuated switch 162. A pressure sensitiveelement 1li-1 communicates with pressure in line 92 for actuation ofpressure actuated switch 102. Normally, pressure sensitive element 101and switch 102 are combined in a single unit, such a unit beingcommercially available.

Details of the pneu-matically operated controller 13 are illustrated inFIGURE 2.

This unit comprises a housing unit 112 in which are provided pistons 113and 117. Piston 113 has a reduced diameter portion indicated at 126. Airpressure in space 114 acts lon the adjacent surface of piston 113. Thearea ot piston 113 facing space 114 is relatively large in comparison tothe area of a circle having as its diameter the smallest diameter ofannular surface 12S. A compression spring 115 is installed asillustrated and biases piston 113 in a direction from left to right.Reference numeral 116 identifies the space from which air from inlet 111presses against piston 117. An O-ring 127 seals space 116 from space114. Piston 117 is attached to shaft 118 as illustrated. Shaft 118 isnot att-ached to piston 113 but instead is free to move independently ofpiston 113 except as hereinafter described. The right-hand end of shaft118 communicates with a compression spring 119, the right-hand end ofwhich is held in position by a nut 128. Nut 128 is provided with athreaded opening 122 for accommodation of a throttle rod 123 (seeFiGURE 1) for actuating the buttery valve of the carburetor 11. Shaft118 is provided with a shoulder or flange 129 for contacting theenlarged end 124 of sleeve 121. A cornpression spring is provided asillustrated for biasing sleeve 121 in a direction from right to left ofFIGURE 2.

In the operation of the pneumatic operated controller 13 of FIGURE 2,high pressure air introduced into space 114 through air inlet 110presses against surface 125 of piston 113 and compresses spring 115 tohold the piston 1.13 against the nut at the left end lof housing 112.Under this condition piston 117 will also move to the left under thepressure of spring 119 and spring 120 will force sleeve 121 to the leftwith the result that the buttery valve of carburetor 11 will be closedto such an extent that the engine will operate at normal idling speed.If air pressure is removed from space 114, as would happen when valve 23(FIGURE 1) is actuated to vent space 114, then piston 113 will be urgedto the right by spring 115. As piston 113 moves to the right, shaft 11Salso moves to the right. When ange 129 contacts enlarged portion 124 ofsleeve 121, sleeve 121 and nut 128 will also move to the right. However,sleeve 121 will move to the right only a short distance because theshoulder of piston 113 will contact or lapproach the right-hand end ofspace 114 and further movement will be prevented. This small amount ofmovement of sleeve 121 is sutcient to open the butterfly valve ofcarburetor 11 a small amount which, in turn, will cause the engine tospeed up to a fast idle. Sufficient engine speed is then available tosupply fluid to the power tongs by way of motor 67. When it is desiredto speed up the engine independently of the fast idle operation justdescribed, high pressure air is admitted to space 116 by way of inlet111. Pressure of the air against piston 117 initially forces the pistonand rod 118 to the right. When flange 129 contacts enlarged end 124 ofsleeve 121, additional air pressure is required to move sleeve 121against the force of spring 120. This additional air pressure lisreadily supplied by throttle valve 17 via pipe 21 and the sleeve 121 ismoved to the right as far as required up to and including the full openposition of buttery valve 11.

FIGURE 3 illustrates in detail construction of the pressure switch 47disposed in electrical circuit 44 or" FIG- URE 1. The working parts ofthis switch are enclosed within a case 140, this case being divided intotwo portions by a flexible diaphragm 151. The portion of the case abovediaphragm 151 represents a uid-tight portion while the portion below thediaphragm may or may not be huid-tight. As used in the apparatus ofFIGURE l the tluid-tight portion of the pressure switch is provided witha threaded opening 147 for accommodation of pipe or line 48. This switchis illustrated in FIGURE 3 of course as being included within circuit44. The upper portion or the fluid-tight portion is sealed againstleakage to the atmosphere by use of a exible sealing washer 148 which isheld in place by a metal or other rigid Washer 149. A rod 141 extendsthrough these several washers and serves as a connection to which onelead of circuit 44 is attached. This rod extends into the casing andterminates as one contact point of a pair of contact points 146. Thesecontact points are normally closed contact points.

kThe lower portion of the switch includes rod 145, to the lower portionof which is connected the other terminal ot`circuit 44. This circuit iscompleted between the lower of the two contact points 146 and rod 145 bya member 142, and metal washers 152 and 144, and spring 143.-

Washer 144 rests upon a iiexible washer 150.

FIGURE 4 is intended to represent a pressure operative switch in generalsimilar to switch illustrated in FIG- URE 3 with the exception that itis a normally open switch. Like reference numerals in FIGURES 3 and 4identify similar pieces of apparatus. Rods 141 and 145, contacts 146a,member 142, spring 143 and washer 144 of FIGURE 4 complete the circuit27a. The normally open contact points are illustrated in FIGURE 4 andare identified by reference numeral 146o. A housing suitable forenclosing the apparatus parts of FGURE 4 is, if desired, similar to thatillustrated in FIGURE 3 and accordingly it will not be described indetail. Flexible diaphragm 151 in FIGURE 4 also separates the portionthereabove as a fluid-tight portion of the pressure switch.

In FIGURE 5 is illustrated, tdigramrnatically and in detail, thesolenoid 3-way valve 23 of FIGURE l. The solenoid 24 is illustrated ashaving one terminal connected to circuit 2.7 and the other terminalgrounded. The valve portion of this solenoid valve is illustrated ashaving a common outlet on one side attached to line 19 and an outletconnected to vent line 22. disposed in such a manner that upon how ofelectrical current through the solenoid the valve is lowered and openedto the iiow of pressure air :from line 19 through the vent line 22. Uponopening circuit 27 the valve raises under the influence of a compressionspring 161 to admit pressure air from line 18 through line 19 to thepressure operated controller 13.

In the operation of this hydraulic system and in reference to FIGURE lthe manually operable switch 46 is closed to energize solenoid 43. Withsolenoid 43 energized valve 39 opens to admit air pressure from pipe 38and tank 35 to rotary coupling or air swivel member 34 and shaft 32 toclutch 31. The application of air pressure to clutch 31 results in shaft32. being coupled with shaft 3G to drive pump 33. The pneumaticallyoperated controller 13 is set so that with switch 46 closed and switch28 open, the motor 10 operates at normal idle speed and drives pump y33at a speed suicient to supply power fluid for the operation of thosehydraulic units which require a comparatively small amount of huid, suchas a derrick raising mechanism, sucker rod tongs, etc.

When switch 2.8 is closed to complete a circuit through solenoid 24,valve 23 is actuated to vent pressure from line 19 through 22. Whensolenoid 24 is energized, the valve portion of the valve 23 movesdownward against compression of spring 161. The venting of air pressurefrom line 19 results in opening the butterfly Valve of the carburetorwith the motor 10 operating at a fast idle speed thereby driving pump 33at a faster speed suiiicient to supply power fluid at a desired rate todrive those hydraulic units requiring a larger amount of rluid, such astubing tongs.

Rotation of shaft 32 drives pump 33 so that hydraulic iiuid is Withdrawnfrom tank 50 through line 51 and de- =livered to line 53 under pressure.A return line 49 is provided 'between pump 33 and tank 50 for return offluid which may leak from pump 33. When it is desired to operate any ofthe auxiliary equipment, not shown, valve 55 is adjusted so that ports54 and 87 are in corn- Inunication as are ports 56 and 9i). The fiuidunder pressure is then transmitted to the auxiliary equipment through aline `S8 and 'is returned therefrom to tank 50 through lines 89 and 83.

In order to energize power tongs in a forward direction, valve 55 is setsuch that ports 54 and 56 are in communication as are ports 37 and 90;Valve 53- is set so that po-rts 57 and 60 are in communication as areports and 81. Valve 63 is set so that ports 62 and 64 are incommunication as are ports 73 and 74. Under these conditions, the fluid`from pump 33 passes through line 53, valve 55, line 59, valve 58, line61, valve 63 and line 66 to the opening 69` of motor 67. Fluid isreturned to tank 50 yfrom motor 67 through opening 76, line 71, valvel63, line 76, check valve 77, line 78, valve 53, line 32 and line `83.When each pipe joint has been tightened it is then necessary to removethe tongs from the pipe.

When the power tongs are employed to unscrew pipe sections valve 58 ispositioned such that ports 57 and 66 are in communication as are portsSi) and 81. Valve 63 is positioned so that ports 62 and 73 are incommunication as are ports 64 and 74. The fluid under pressure is thentransmitted from line 59l through valve 53, line 61, valve 63, and line71 to port 76 of motor 67. Fluid is returned to tank 50 through line 66,valve 63, line 7 6, check valve 77, line 78, valve 58, lines 82 and line33. In order to center the tubing tongs when operated irthe reversedirection, valve 58 is reversed. Fluid is then transmitted -from line 59to valves 5S, line 7S, centering stop valve 85, line 76, valve 63 andline 66 to port 63 of motor 67. The return iiuid is transmitted to tank5@ through line 71, valve 63, line 61, valve 5S, lines 82 and 33.

A Isecond power take-Off 12 is provided near the drive shaft end ofengine 10. This power take-orf provides power for pulling casing and forsuch other uses as require high engine speeds with a mechanical directdrive takeoff, that is, a non-hydraulic drive.

The handle of the reversing valve 63 has a neutral position intermediateits line of movement. When this valve handle is in its right handposition pipes 61 and 66 are connected and pipes 71 and 76' areconnected to permit ilow of hydraulic fluid through motor 67 in onedirection. When this valve handle is moved to the left of the centerneutral, the motor 67 is reversed by closing oit flow of uid through thepipes just mentioned and connecting pipes 61 to 71 and pipes 66 to 76.In the valve handle neutral or center position pipe 61 is connected topipe 76 to by-pass completely the motor 67. This by-pass involvespassage of hydraulic tluid from pump 33 through pipe 53, valve 55, pipe59, valve 58, pipe '61, valve 63, pipe 76, check valve 77, pipe 78,valve 58, pipe S2 and pipe 83 to storage 50. tIn this manner thehydraulic liquid is performing no useful work and the pressure from pumpto storage is merely that caused by flow through the just mentionedpipes and valves. However, when valve 63 is actuated to operate motor67, the pressure drop from pump to storage is markedly increased due tothe load on motor 67 for operating power tongs, for example. With switch28 and circuit 27 open and switch 103 in circuit 27a closed, thisincrease in pressure drop from pump to storage is evidenced in line 92by an increase in pressure therein. This increase in pressure is sensedby the pressure sensing apparatus 101, and switch 162 is closed thereby,thus venting pressure air from line 19 through the solenoid valve 23 andvent line 22. Upon venting pressure air from line 19, the pneumaticoperated controller 13 actuates to allow movement to a piston assembly112e to the right which movement increases somewhat the ilow of fuel tothe engine. Sudicient engine speed is then available to supply fluid tothe power tongs by way of motor 67. If it is desired to pull tubing,throttle valve 17 is opened to admit pressure air to line 21 and thencethrough inlet 111 to piston 117 of pneumatic controller 13 to increaseengine speed. Upon opening throttle valve 17 pressure air flows frompipe 21 through pipe 4810 actuate pressure switch 47 to disengage clutch31 so that pump 33 will be inoperative. It is immaterial whether switch103 is opened or closed when switch 28 is closed because the latteroverrides action of the pressure assembly i-102 in maintaining valve 23in its venting position. Y

By providing circuit 27a with a pressure switch assembly 101-102, themotor is automatically speeded up an amount sufficient to supply justenough hydraulic fluid from pump 33 to operate power tongs or otherhydraulically operable equipment without overspeeding pump 33. By theuse of this invention I am able to use hydraulic pump 33 as long as 24to 30 months between overhaul periods in contrast to need for pumpoverhauling each 3 to 6 months when my invention is not used.

While certain embodiments of the invention have been described forillustrative purposes, the invention obviously is not limited thereto.

I claim:

l. A control system for regulating the speed of a variable speed drivingmember comprising, in combination, a Variable speed driving memberhaving an actuating iiuid flow control valve in operative communicationwith said driving member, a hydraulic iiuid pump driven by said drivingmember, a pneumatically operable spring biased controller operativelyconnected with said actuating iluid 5 ow control valve, a source ofpneumatic fluid under a superatmospheric pressure, a rst conduitcommunicating said source of pneumatic lluid under pressure with saidcontroller, a 3way solenoid valve in said conduit, a source ofelectromotive force, an electrical circuit communicating said source ofelectromotive force with the solenoid of said valve, a second conduitleading from said pump for transmission of hydraulic fluid underpressure, a pressure switch, the switch of said pressure switch beingdisposed in said circuit, the pressure sensing element of said pressureswitch being in operative communication with said hydraulic fluid insaid second conduit, said pressure sensing element being adapted toclose said switch in response to a predetermined pressure of saidhydraulic iuid in said second conduit above a pressure produced by a lowidling speed of said driving member thereby causing said 3-way valve tovent pneumatic iluid from said controller whereby said spring biasesopen said actuating fluid flow control valve to increase the speed ofsaid driving member to a fast idling speed, and said pressure sensingelement being adapted to open said switch in response to a pressurebelow said predetermined pressure of said hydraulic fluid in said secondconduit thereby causing said 3-way valve to open said -rst conduit to 8said controller thereby admitting pneumatic iiuid under pressure to saidcontroller thereby actuating said spring loaded controller against itsbias' and throttling said actu-ating -iluid flow control valve todecrease the speed of said driving member to a normal idling speedthereby providing said hydraulic i'luid under suiiicient pressure onlyfor light duty service.

2. A control system to regulate speed of a variable speed driving membercomprising, in combination, a variable speed driving member, a hydraulicfluid pump driven =by said driving member, a source of pneumatic fluid,a spring loaded pneumatic controller, a iirst conduit communicating saidsource of pneumatic iluid under pressure with said controller, saidpneumatic controller being operatively connected with said drivingmember for regulating ilow of fuel thereto, an electrically operative3-way motor valve in said rst conduit, a source of electromotive force,an electrical circuit communicating said source of electromotive forcewith the motor of said motor valve, a second conduit operablycommunicating said pump with a point of hydraulicV huid use, a hydraulicuid, in said pump and said second conduit, a pressure switch having apressure sensing element operatively connected therewith, the switch ofsaid pressure switch being disposed in said electrical circuit and saidpressure sensing element being in operative communication with saidsecond conduit, said 3-way valve having a vent, said pressure sensingelement upon sensing a pressure higher than a predetermined pressureclosing the switch oi the pressure switch to complete said electricalcircuit to the motor of said motor valve thereby communicating saidiirst conduit intermediate said pneumatic controller and said 3-wayvalve with said vent whereby the spring of said controller biases saidcontroller in such a manner as to increase the speed of said drivingmember to a fast idling speed and provides high pressure hydraulic iluidfor heavy duty service, and said pressure sensing element upon sensing apressure below said predetermined pressure opens said switch therebyopening said electrical circuit and thereby communicating said rstconduit intermediate said pneumatic controller and said 3-way valve withthe first conduit intermediate said 3way valve and said source ofpneumatic uid whereby said pneumatic fluid biases said spring of saidcontroller in such a manner as to decrease the speed of said drivingmember to a normal idling speed thereby providing hydraulic fluid belowsaid predetermined pressure for normal light duty service.

3. An internal combustion engine throttling control assembly comprising,in combination, a variable speed internal combustion engine, la throttlevalve in operative communication with said engine, a pneumaticallyoperable spring loaded controller, said controller being operativelyconnected with said throttle valve, a source of pneumatic iluid underpressure, a rst conduit communicating said controller with said sourceof pneumatic fluid under pressure, an electrically operative 3-way motorvalve in said conduit, a source of electromotive force, an electricalcircuit communicating said source of electromotive force with the motorof said valve, a pressure switch having a pressure sensing elementoperatively connected with the switch, a hydraulic pump operativelyconnected lwith said engine, a hydraulic pressure restricting means, asecond conduit communicating said pump with said pressure restrictingmeans, hydraulic iiuid in said pump and in said second conduit, saidswitch being disposed in said circuit, said pressure sensing elementoperatively communicating with said second conduit and being adapted toclose said switch on sensing a pressure above a predetermined pressurethereby Vactuating said motor valve to vent pneumatic iluid underpressure from said controller and actuating said spring loadedcontroller References Cited in the tile of this patent UNITED STATESPATENTS Ferris etal. Mar. 12, 1918 Dolza et al. Aug. 14, 1951 -FooteOct. 5, 1953 Province Feb. 12, 1957 Henz Mar. 5, 1957

